With the development of information technology, information encryption has been widely used. Since the Liquid Crystal Display (LCD) is a major carrier for displaying image information, how to encrypt displayed images on the liquid crystal display is becoming more and more important. The conventional video signal encryption technology has a good security in signal transmission and signal preservation, but cannot achieve real-time viewing. In addition, an existing encryption technology realizes an encryption function by removing a polarizer of the liquid crystal display so that the liquid crystal display can only display a white bright field, but in practice, the displayed images could be viewed as long as the polarizer is available, and therefore this encryption technology has a poor security.
In another encryption technology, a good security is expected by adhering a phase delay film to the liquid crystal display to cause the displayed images on the liquid crystal display to be distorted, and in the meantime, adhering a depolarization film to the polarized glasses. However, the displayed images could be viewed only by wearing the same glasses. The displayed images could be acquired by trying films having different delay amounts to find an appropriate delay amount, and therefore this encryption technology also has a poor security.